/Users/deen/code/yugabyte-db/src/yb/server/clock.h

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#ifndef YB_SERVER_CLOCK_H_
#define YB_SERVER_CLOCK_H_

#include <functional>
#include <string>

#include "yb/common/clock.h"
#include "yb/common/hybrid_time.h"

#include "yb/gutil/ref_counted.h"

#include "yb/util/status_fwd.h"
#include "yb/util/monotime.h"

namespace yb {
class faststring;
class MetricEntity;
class MonoDelta;
class Slice;
class Status;
namespace server {

// An interface for a clock that can be used to assign timestamps to operations.
// Implementations must respect the following assumptions:
// 1 - Now() must return monotonically increasing numbers
//     i.e. for any two calls, i.e. Now returns timestamp1 and timestamp2, it must
//     hold that timestamp1 < timestamp2.
// 2 - Update() must never set the clock backwards (corollary of 1).
class Clock : public ClockBase {
 public:

  // Initializes the clock.
  virtual CHECKED_STATUS Init() = 0;

  // Update the clock with a transaction timestamp originating from
  // another server. For instance replicas can call this so that,
  // if elected leader, they are guaranteed to generate timestamps
  // higher than the timestamp of the last transaction accepted from the
  // leader.
  virtual void Update(const HybridTime& to_update) = 0;

  // Register the clock metrics in the given entity.
  virtual void RegisterMetrics(const scoped_refptr<MetricEntity>& metric_entity) = 0;

  virtual ~Clock() {}
};

typedef scoped_refptr<Clock> ClockPtr;

template <class Request>
void UpdateClock(const Request& request, Clock* clock) {
  auto propagated_hybrid_time = HybridTime::FromPB(request.propagated_hybrid_time());
  // If the client sent us a hybrid_time, decode it and update the clock so that all future
  // hybrid_times are greater than the passed hybrid_time.
  if (!propagated_hybrid_time) {
    return;
  }
  clock->Update(propagated_hybrid_time);
}

} // namespace server
} // namespace yb

#endif /* YB_SERVER_CLOCK_H_ */

YugabyteDB (2.13.1.0-b60, 21121d69985fbf76aa6958d8f04a9bfa936293b5)

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Created: 2022-03-22 16:43